Unless otherwise indicated herein, the description provided in this section is not itself prior art to the claims and is not admitted to be prior art by inclusion in this section.
A cellular wireless network may include a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or a packet-switched network such as the Internet for instance. With this arrangement, a UE within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs.
When a UE first enters into the coverage of a cellular wireless network, the UE engages in a process of registering or “attaching” with the network, which may trigger setup of various communication channels for the UE and/or reservation of various communication resources for the UE. For instance, upon first detecting coverage of a base station, the UE may transmit an attach request message to the base station, which the base station may forward to a network controller such as a mobility management entity (MME). Upon authenticating and authorizing the UE, the network controller may then engage in further signaling with the base station and with a serving gateway (SGW), which may in turn engage in signaling with a packet data network gateway (PGW), ultimately resulting in setup of one or more bearer connections or “bearers” each extending, via the base station, between the UE and the PGW, through which the UE can then engage in packet-data communication via the PGW.
Each bearer established for a UE may define a logical communication tunnel that includes a radio bearer portion extending between the UE and the base station, and an access bearer portion extending between the base station and the PGW via the SGW. Further, each bearer may have a designated quality of service level, which may dictate how the packet data transmission along the bearer is handled by the network. For instance, a bearer could have a relatively high quality of service level, according to which network nodes (such as the base station, SGW, and various routers) along the bearer path could be set to prioritize routing of data on the bearer over routing of data on other bearers, perhaps to guarantee a particular minimum bit rate, a particular maximum level of packet delay, and/or a particular maximum level of packet loss. Alternatively, a bearer could have a relatively low quality of service level, such as a “best efforts” service level, according to which nodes along the bearer path would simply do their best to route data of the bearer, subject to higher priority handling of other bearer traffic.
In practice, a network such as this may initially establish for a UE one or more default bearers to enable the UE to engage in certain basic communications, with each default bearer having a respective quality of service level. By way of example, the network may initially establish for the UE a default Internet bearer with a best-efforts quality of service level, for use by the UE to engage in general Internet communications such as web browsing, e-mail messaging, and the like. Further, if the UE subscribes to voice over Internet Protocol (VoIP) service or another such service that would be served by an Internet Multimedia Subsystem (IMS) platform, the network may initially establish for the UE a default IMS signaling bearer with a medium quality of service level, for use by the UE to engage in session setup signaling (such as Session Initiation Protocol (SIP) signaling) with the IMS to facilitate setup of VoIP calls or the like.
As the UE is served by the network, the network may also establish for the UE additional bearers as needed. For example, if the UE has an IMS signaling bearer and the UE engages in signaling over that bearer with an IMS to set up a packet-based real-time media session such as a VoIP call, the network may then establish for the UE a dedicated IMS bearer with a high quality of service level, for carrying media content of the session, such as VoIP voice packets, to and from the UE. Once the dedicated IMS bearer is established, the UE may then send and receive media content of the session over that dedicated IMS bearer.
When a UE is served by a base station, the UE may regularly monitor the reference signal from that base station and reference signals from other base stations in the vicinity, to help ensure that the UE continues to operate in a most appropriate coverage area. If the UE finds that one or more other base stations provide sufficiently strong coverage, perhaps sufficiently stronger than the UE's currently serving base station, then the UE may initiate handover. For instance, the UE may transmit to its serving base station a measurement report that specifies the one or more detected coverage areas and, for each such coverage area, the detected signal strength. The serving base station (source base station) and/or associated network infrastructure may then decide based on the UE's measurement report to process a handover of the UE to a particular base station (target base station) from which the UE detected sufficiently strong signal strength.